The present invention relates generally to passenger restraint systems in vehicles. More specifically, the present invention relates to a passenger restraining seat assembly for a bus.
Automotive vehicles commonly have three-point seat belt systems that combine a lap belt and an upper torso belt. In these systems, the tongue is swung across the person and is engaged with a buckle affixed to the seat to position one portion of the belt across the lap and another portion of the belt across the upper torso.
In school buses, however, passive restraints are commonly used. Passive restraints are restraints which do not positively restrain the occupant, but which impede the motion of the occupant within a compartment or space. The use of three-point belts in buses is not commonly incorporated because the safety requirements involved with three-point belt installation may actually conflict with the requirements for passive restraints. The U.S. federal government requirement for passive restraints requires that the rear side of the seat provide an impact barrier in which the seat back bends or deforms when subjected to the force of occupants impacting the rear side in a deceleration event. The National Highway Traffic Safety Administration, DOT (NHTSA), sets the federal requirements for these passive restraints. These are codified as 49 C.F.R. Section 571.222 (FMVSS 222).
The code specifies a passive restraint system, and does not require any sort of active restraints such as a two-point passenger restraining lap belt or a three-point passenger restraining lap belt and torso harness combination. The passive restraint requirement effectively provides a compartment in which an unbuckled passenger is constrained during a rapid deceleration of the bus. Although two point belt systems are offered on buses, designers need to consider three-point seat belts where there is a request for them through local, state, or transportation/parental action groups. Three-point seat belt designs are also regulated under NHTSA code. These requirements relate to belts that are mounted in such a fashion that they inhibit a belted passenger's forward movement. This three-point belt-mounting requirement is codified in 49 C.F.R. Sections 571.209 and 571.210 (FMVSS 209 and FMVSS 210).
The conflict in installing three-point seat belts on bus seats is that when the three-point belt is installed, the strength of the seat for receiving impact from the occupant behind the seat is reduced. Tests have shown that in a rapid deceleration where the passenger in the front seat is buckled and the passenger in the rear seat is not buckled, the initial action is that the buckled passenger moves forward applying tension on the buckled seat belt and the component of the seat that the belt is affixed to. This results in a pulling of the fixture component in a forward direction, thereby reducing the strength on the rear impact face, and/or positioning the rear impact face of the seat forward. Following the tension applied on the three-point belt, the rear passenger likely impacts the weakened and/or displaced seat back. The reduction in seat back strength and/or change in location due to the pull on the three-point seat belt for FMVSS 210 requirements may reduce the ability of the seat back to meet the FMVSS 222 requirements.
Recent school bus seat designs have been developed that involve a pivotable inner seat for the mounting of the three-point seat belts and an immovable seat back portion for the absorption of the rear unbuckled passenger loads. The pivotable inner seat was inserted into a recess within the seat back. The seat back would be designed to deform in order to comply with FMVSS 222, while the front portion of the seat would pivot forward. Some of these designs were disclosed in U.S. Pat. Nos. 6,123,388, 6,485,098, and 6,953,223. The concept of a seat inserted within a seat was not new and was disclosed in U.S. Pat. No. 4,784,352.
Thus, there is a need for a seat that meets the various federal requirements without pivoting the front portion of the seat.